1. Field of the Invention
The invention relates to an implantable medical device such as an anastomosis device and a deployment system for implanting the device. In a preferred embodiment, the device can be used for forming a sutureless connection between a bypass graft and a blood vessel.
2. Brief Description of the Related Art
Vascular anastomosis is a procedure by which two blood vessels within a patient are surgically joined together. Vascular anastomosis is performed during treatment of a variety of conditions including coronary artery disease, diseases of the great and peripheral vessels, organ transplantation, and trauma. In coronary artery disease (CAD) an occlusion or stenosis in a coronary artery interferes with blood flow to the heart muscle. Treatment of CAD involves the grafting of a vessel in the form of a prosthesis or harvested artery or vein to reroute blood flow around the occlusion and restore adequate blood flow to the heart muscle. This treatment is known as coronary artery bypass grafting (CABG).
In the conventional CABG, a large incision is made in the chest and the sternum is sawed in half to allow access to the heart. In addition, a heart lung machine is used to circulate the patients blood so that the heart can be stopped and the anastomosis can be performed. During this procedure, the aorta is clamped which can lead to trauma of the aortic tissue and/or dislodge plaque emboli, both of which increase the likelihood of neurological complications. In order to minimize the trauma to the patient induced by conventional CABG, less invasive techniques have been developed in which the surgery is performed through small incisions in the patients chest with the aid of visualizing scopes. Less invasive CABG can be performed on a beating or stopped heart and thus may avoid the need for cardiopulmonary bypass.
In both conventional and less invasive CABG procedures, the surgeon has to suture one end of the graft vessel to the coronary artery and the other end of the graft vessel to a blood supplying vein or artery. The suturing process is a time consuming and difficult procedure requiring a high level of surgical skill. In order to perform the suturing of the graft to the coronary artery and the blood supplying artery the surgeon must have relatively unobstructed access to the anastomosis site within the patient. In the less invasive surgical approaches, some of the major coronary arteries including the ascending aorta cannot be easily reached by the surgeon because of their location. This makes suturing either difficult or impossible for some coronary artery sites. In addition, some target vessels, such as heavily calcified coronary vessels, vessels having very small diameter, and previously bypassed vessels may make the suturing process difficult or impossible.
An additional problem with CABG is the formation of thrombi and atherosclerotic lesions at and around the grafted artery, which can result in the reoccurrence of ischemia. The thrombi and atherosclerotic lesions may be caused by the configuration of the sutured anastomosis site. For example, an abrupt edge at the anastomosis site may cause more stenosis than a more gradual transition.
Accordingly, it would be desirable to provide a sutureless vascular anastomosis device which easily connects a graft to a target vessel. It would also be desirable to provide a sutureless anastomosis device which is formed of one piece and is secured to the target vessel in a single step.
According to a preferred embodiment, the present invention relates to an anastomosis device for connecting an end of a graft vessel to a target vessel wherein the device cooperates with a deployment tool for connecting an end of the graft vessel to the target vessel. The anastomosis device comprises a first linkage deformable by the deployment tool to form a first flange (e.g., an inner flange which connects the graft vessel to an inner surface of the target vessel), an optional connecting portion extending from the first linkage, and a second linkage deformable by the deployment tool to form a second flange (e.g., an outer flange which connects the graft vessel to an outer surface of the target vessel), the second linkage including deformable links which cooperate with a distal end of the deployment tool to form the second flange. The anastomosis device is preferably sized to fit through an incision in the target vessel such that the first flange comprises an inner flange which presses a portion of the graft vessel into intimate contact with an inner surface of the target vessel and the second flange comprises an outer flange which presses another portion of the graft vessel into intimate contact with an outer surface of the target vessel.
The anastomosis device can include various features. For instance, a connecting portion can be provided between the first and second linkages and the first and second linkages can include axial members having weakened areas which cause the axial members to bend simultaneously during formation of the inner and/or outer flange. The deployment tool can include an expander which forms the first flange and a holder tube surrounding the expander, the holder tube engaging the deformable links and bending the deformable links outwardly to form the second flange.
The deployment tool can incorporate various features. For example, a deforming crown tool can include first members and the deformable links can include second members which remain connected to the first members during formation of the first flange and disconnect from the first members during formation of the second flange, the deformable members bending the deformable links outwardly during formation of the second flange and returning to a non-bent configuration after formation of the second flange. The first members can comprise tabs and the second members can comprise slots which engage the tabs and openings which disengage the tabs, the slots extending from the openings towards a proximal end of the anastomosis device. A deforming crown deployment tool can include deformable members at the distal end thereof, the deformable members being plastically deformed after bending the deformable links outwardly to form the second flange. In a third embodiment, the deployment tool breaks off part of the anastomosis device during formation of the outer flange. For example, the anastomosis device can include a deployed portion (implant) and a severable portion (discard) wherein the first and second flanges are formed on the deployed portion and the severable portion is severed from the deployed portion when the second flange is formed. The deployed portion can be connected to the severable portion by shearable connectors and the shearable connectors can be located at pivot connections between the deployed portion and the severable portion. The severable portion and the deployed portion are preferably machined from a single piece of metal and the pivot connections can comprise thin sections of the metal extending between the deployed portion and the severable portion.
The anastomosis device can incorporate various structural features. For instance, the first linkage can include a plurality of struts arranged in a configuration such that an axial dimension of the first linkage changes upon radial expansion of the first linkage. Further, the first linkage can include a plurality of piercing members which penetrate the graft vessel. The second linkage can include a plurality of axial members and struts arranged in a configuration such that radial expansion of the second linkage does not cause formation of the second flange. The second linkage can also include pairs of axial members which are closer together at a distal end thereof than at a proximal end thereof, the proximal ends of the axial members being joined by circumferentially extending severable links to a linkage supported by the tool, the severable links being severed when the second flange is formed.
An anastomosis device deployment system according to the invention can include a handle and a holder tube attached to the handle, the holder tube having a distal end configured to hold the anastomosis device with an attached graft vessel; and an expander positioned within the holder tube and slidable with respect to the holder tube to a position at which the expander is positioned within the anastomosis device and radially expands the anastomosis device. The system can further include a trocar movable with respect to the holder tube to form an opening in a target vessel to receive the anastomosis device and attached graft vessel. The trocar can be a split trocar which is slidable over the holder tube and the expanded anastomosis device. The handle can include cam grooves which cooperate with followers of the holder tube and expander to move the holder tube and expander with respect to one another upon activation of a trigger of the handle. The distal end of the holder tube can include a plurality of slits, loops and/or flexible fingers for engaging tabs of the anastomosis device during formation of the inner and outer flanges.
According to another embodiment of the invention, the frangible linkage can be used to release an implant portion of a medical device at a target site in a living body. According to this embodiment, the medical device cooperates with a deployment tool for delivering and deploying the medical device to the site. The medical device includes first and second sections connected together by a frangible linkage, the frangible linkage being deformable by the deployment tool such that frangible elements of the frangible linkage are broken and the first section is separated from the second section. The frangible elements can include weakened areas which cause the frangible elements to bend when the frangible linkage is deformed by the deployment tool. For instance, the medical device can comprise an anastomosis device and the first section can include hinged axial members which bend outwardly and form first and second flanges. The deployment tool can include an expander which forms the first flange and a holder tube surrounding the expander, the holder tube engaging the second section and forming the second flange while separating the first section from the second section.